Some known systems sense vibrations propagating through the ground in order to detect the presence of one or more objects. These systems can examine the vibrations that are sensed in order to attempt to identify the objects, determine where the objects are located, and the like. One example of such systems senses ground vibrations using a fiber optic cable extending beneath or near rail tracks. While these fiber optic cables may have been placed along the rail track to provide network connectivity, some rail companies have the ability to use these fiber optic cables to monitor vibrations in the ground. These vibrations can be used to attempt to identify the passage of rail vehicles along the track.
One problem with these known systems is that the systems are not “vital” systems. For example, the systems may be unable to automatically correct changes in sensed vibrations that are caused by external factors. Changes in the weather and other factors may change the vibrations and/or the propagation of vibrations through the ground, and can hinder or block the ability of these systems to accurately identify rail vehicles based on the vibrations that are generated. These systems may suffer from incorrectly detecting a rail vehicle based on vibrations that are not caused by the rail vehicle, but that appear to be caused by a rail vehicle due to the impact of environmental conditions on the propagation of the vibrations. Similarly, these systems may suffer from failing to detect a rail vehicle based on vibrations that are caused by the rail vehicle, but that do not appear to be caused by a rail vehicle due to the impact of environmental conditions on the propagation of the vibrations.
Additionally, existing systems typically rely on a one-time calibration of the exact location of the fiber optic cables. Changes in the fiber optic cable or interrogation equipment subsequent to calibration, therefore, can introduce errors into the data utilized to detect vehicles. For example, if the fiber optic cable characteristics or the fiber optic cable itself is moved, data skewing can occur and the accuracy of the system can be affected. Accordingly, there is a need for a system and method that is capable of ensuring that the physic fiber optic cables have not moved, and which can be calibrated to account for any such movements.